Contact assembly



July 6, 1937. c. a. GWYN, JR 2,085,221

' conmc'r ASSEMBLY- Filed Dec. 10, 1934 INVENTOR flulg mss A". fiwgn, J2

ATTORN EY Patented July 6, 19 37 PATENT [OFFICE CONTACT ASSEMBLY Childrcss B. Gwyn, Jr., Indianapolis, Ind., as-

signor, by mesnc assignments, to P. R. Mallory & Co. Inc., Indianapolis, Ind., a corporation of Delaware Application December 10, 1934, Serial No. 756,733

7 Claims.

taneous application of pressure and electric current to the component parts of the contact assembly during assembling thereof whereby portions thereof are interfused. Furthermore, the component parts may be so shaped and prepared as to provide interlocking surfaces. Reservoir space may also be provided in the parts for any excess flow of metal developed during assembly.

The invention accordingly comprises the features of construction, combination of elements and arrangement of parts, referred to above or which will be further brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawing, the scope of the invention being indicated in the appended claims.

For a fuller understanding of the nature and objects of the invention as'well as for specific fulfillment thereof, reference should be had to the following detailed description taken in connection with the accompanying drawing, in which;

Figure 1 is a top view of a contact member adapted for incorporation into a contact assembly.

Figure 2 is a side view of the contact member shown in Figure 1;

Figure 3 is a top view of a base or support member suitable for assembly with the contact member shown in Figures 1 and 2;

Figure 4 is a side view of the base member shown in Figure 3;

Figure 5 is a section on the line 5-5 of Figure 4;

Figure 6 is a diagrammatic illustration of the component parts of the contact assembly and part of the assembly machine during the assembling operation;

Figure '7 is a side view of a completed contact assembly; and

Figure 8 is a view, partly in section, of the completed. assembly.

, Like reference characters indicate like parts in the several figures of the drawing.

While a preferred embodiment of the invention will be described herein, it is contemplated that considerable variations may be made in the method of procedure and the construction of parts without departing from the spirit of the invention.

Referring, now, more particularly to the drawing wherein one embodiment of the invention is illustrated, a contact member or rivet i0 is shown in Figures 1 and 2 having a disc-shaped head ll of non-refractory contact material, such as fine silver, for example, and a cylindrical shank 52 formed integrally therewith of the same material or of a difierent metal, alloy or composition. Contact member lil may be prepared by any standard and well known method such as by upsetting or heading.

A suitable base or support blank 93, for supporting contact member it after assembling is shown more particularly in Figures 3 to 5. This comprises a portion it threaded or otherwise adapted to be secured in a suitable manner and position in electrical apparatus where the contact assembly is intended for use, and a recessed portion i5 adapted to receive contact member l0. Portion M may likewise be provided with a screw driver slot til or other means for adjusting the contact assembly in the electrical apparatus. Portion it has a tapped or threaded hole or recess [l6 therein of substantially the same diameter as shank I2, or of slightly smaller or larger diameter, as desired, and is intended to receive shank i2 upon assembly. Portion i5 is provided with a substantially plane end surface I! surrounding the mouth of hole l6 and adapted to serve as a seat for the underside of head II of the contact member i 0.

A circular ridge i8 is formed on surface i1 and encircles the mouth of hole l6. Ridge l8 provides for correct seating of contact member ill on base member l3 and also provides for a reseri voir space to receive any excess flow of metal during assembly and thereby prevent foreign metals from reaching the upper contact surface.

Base member 43 may suitably be made of any 1 desired metal or material commonly used in electrical parts such as brass or steel, for example. The material is preferably one which is harder and has a higher melting point than the contact material. i

The method of assembly may be as follows:

Shank 12 of contact member I0 may be placed in the mouth of hole I6 in base member I5 and axial pressure may be applied in any suitable manner such as by the press comprising plunger I9 and support 20 (Figure 6). Simultaneously with the application of pressure an electric current of high density but of low voltage is passed through the assembly from the face of head I I of the contact rivet I II to the body of base member I3.

The current may be supplied in any desired manner and may be either alternating or direct current. Alternating current may present some advantage over direct current since it lends itself to more accurate timing control by means of a thyratron control system. The current may suitably be supplied, for example, as shown diagrammatically in Figure 6 by a step-down transformer 2| from the commercial alternating current supply. In this instance one low voltage terminal isconnected to plunger I9 and the other terminal to support 20. Current regulating equipment, shown as a variable resistance 22 is included in the circuit for controlling the current intensity and switching equipment shown diagrammatically as contacts 23, is provided for starting and stopping the flow of current. A timing control 24 is preferably associated with the switching equipment for controlling the the transformer.

duraticn of the current flow. The above described electrical system is intended to be merely illustrative of the general arrangement of parts and is in no sense intended to be limiting as to the type of equipment used or the mode of operation thereof. Thus the switching and control might be carried out on the high voltage side of The timing equipment might preferably comprise a thyratron control system.

The current is preferably so controlled in intensity and duration as to heat shank I2 to the point of softening. Since the current density is greater in shank I2 than in the head II of the control rivet or the body of base member I 3 these parts are not appreciably softened by the current. As the current softens shank I2 the pressure applied by plunger I9 forces the shank into hole I6. The softened material of the shank flows into the thread grooves of hole I6, to form an interlocking structure.

After the shank I2 has been forced entirely into the hole I6 so that contact head II seats squarely against ridge I8 on surface I! the current is continued foran additional short period to bring about an interfusing or alloying of the material of the shank and of the threaded portion of hole I6, thereby forming an autogenous weld between these parts. This current may also cause a. fusing of ridge I8 into the bottom surface of contact II to further unite the contact head and backing member.

Should shank I2 inadvertently be made slightly oversize or overlength so as to provide more than suflicient metal to fill hole I6 the excess metal may flow out of the hole and be received in the reservoir space formed by ridge I8 surrounding the hole. Thus the excess metal will be kept from flowing to the upper contact surface. Normally, however, when there is no excess metal, ridge I8 is fused into the bottom surface of contact head II so closely that head I I will seat directly against surface I1.

The completed contact assembly is shown in Figure 'I and illustrated in section in Figure 8.

As an example of the values of current, voltage, time and pressures required for making an assembly in actual practice, the following were found to give satisfactory results:

On a contact assembly having a contact face of .125" diameter, of fine silver, a shank diam eter of .078" and a commercial brass screw backing, using a 356 thread in the center, the instantaneous current, as read on an oscillograph, was 500.amperes A. C., the voltage applied to the assembly was 3.5 volts A. C. and the time the current was applied was 1 cycle A. C. or 1/60 second, governed by a thyratron control. The pressure applied to the surface of the contact rivet ID was 25 pounds.

Wide variations may be made, of course, in the practice of the invention both as to the form and structure of the component parts of the contact assembly, the type of assembling machinery used and the details of the assembly method. It is contemplated, for example, that the threading may be cut on the shank portion I2 instead of in hole I 6, and that the hole and shank may be reversed in position, that is, the hole may be provided in the contact member and the shank in the backing member, if desired.

The present invention shows a marked improvement over previous contact assemblies and methods of making them. The method is well adapted to practical production giving superior and more economical results than former methods of brazing, welding, mechanical staking or force fitting. When the relatively simple operation described above is completed there is little or no further processing required beyond inspection.

The adjacent surfaces of the contact member and the base member are united by an autogenous weld of low resistance. The weld prevents the occurrence of electrolytic corrosion or battery action between the surfaces of the two metals.

Since no lower melting brazing or welding materials are used, there is little danger of the creeping of foreign materials to the contact surface. Furthermore, any excess metal flow developed during production will beheld in the reservoir space and prevented from reaching the contact surface.

The contact assembly parts are both welded together and interlocked rendering impossible any loosening after repeated mechanical hammering or vibration or repeated expansion and contraction due to variations in temperature. The interlocking and welding arrangement likewise makes possible a shorter shank length than with purely mechanical staking methods.

While the present invention, as to its objects and advantages, has been carefully described herein as carried out in a specific embodiment thereof, I do not desire to be limited thereby but intend to cover the invention broadly within the spirit and scope of the appended claims.

I' claim:

1. A contact-support blank having a recessed portion for receiving a projection on a contact part, said recessed portion having formations for interlocking with said projection and having a reservoir for receiving excess metal.

2. A contact support blank having a hole in one of its surfaces for receiving a projecting shank of a contact part and a continuous ridge on said surface encircling the mouth of said hole. a

3. A contact assembly comprising a contact part and a supporting part, one of said parts having a shank portion and the other of said parts having a recessed portion receiving said shank portion, one of said portions being threadacsaaar ed. and an interfused iunction between said shank portion and said recessed portion.

d. A. contact assembly comprising a silver contact part and a base metal supporting part, one of said parts having a shank portion and the other oi. said parts having a recessed portion re-= ceiving said shank portion, one of said portions being threaded, and an interfused junction be tween said shank portion and said recessed por-- tion.

5. A contact backing blank having a substantiaily plane face and a depression in said face, circular disconformity in said surface surroundins said depression and spaced therefrom, said disconi'ormity comprising a deviation of the sur= race from the plane of said face whereby said disconiormity is adapted to stop the flow of molten contact metal outward from said depression,

"5., A contact backing blank of steel having a substantially plane face and a depression in said face, a circular disconiormity in said surface surrounding said depression and spaced therefrom, said disconformity comprising a deviation of the surface from the plane of said face where-.- by said disconformity is adapted to stop the flow of molten contact metal outward from said depression.

if. A contact assembly comprising a steel back ing member and a silver contact member fused thereto, the interface between said backing and contact members being characterized by a depression in said steel backing into which said silver extends, a substantially flat interface area surrounding said depression and a flow-restricting disconformity in said interface surroundin said flat area, said disconformity comprising a deviation of the interface from the plane of said fiat area,

@i-IEDRESS B. GWYN, J's. 

